EXP 4: Grignard PDF

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Experiment 4: Grignard Reagent This experiment was designed to use an organometallic reagent in a synthesis reaction and be able to correctly identify the starting compounds through retrosynthetic analysis. There are some safety concerns with the ether solvents used in this lab, since they are highly flammable and react readily with atmospheric oxygen. This forms peroxides, which can produce an explosion. To prevent some serious hazards, not distilling to dryness is an important part of this lab. Grignard reagents react with water to produce an alkane, which will prevent a successful experiment resulting in a tertiary alcohol. THF is also very flammable and a volatile liquid, so keeping the equipment underneath the hood reduces the hazards of a fire. The reaction between alkyl or aryl halides and magnesium results in Grignard reagents. The lab conducted had three possible alkyl halides including 1-bromopropane, 1-bromobutane and 1-bromopentane. There were four potential ketones that were selected at random including acetone, butanone, 2pentanone and 3-pentanone. The Grignard reaction results in alcohols, primary, secondary or tertiary depending on the starting materials. Since the starting materials for this lab is alkyl halide, a tertiary alcohol is the end product. The Grignard reagent was synthesized by reacting an alkyl bromide with magnesium. Grignard reagents are also strong bases, and they’re great nucleophiles.

The boiling point of the compounds ranges from 2-methyl-2-pentanol at 122 ℃ to 4methyl-4-nonanol at 212 ℃ . The assigned alkyl halide has a melting point range from 108-113 ℃ . This indicates that it is 1-bromopentane. The ketone used was most likely 3-pentanone. The product that this reaction produces is 3-ethyl-3-hexanol. The molar mass of this compound is

130.23 g/mol. Since the original mass of Mg was 0.61 g, which is 0.025 mol, the end product should be 0.025 mol. The theoretical yield for this reaction is 3.256 g, the actual yield is 0.499 g. This means the percent yield is 15.33%. This reaction is one of many considering Grignard reagents. Another synthesis combination method would be to use 1-bromopropane and 2-pentanone to produce 4-methyl-4heptanol....